A green roof is a roof of a building that is partially or completely covered with vegetation and growth media planted over a waterproofing membrane. Examples of the growth media are soil, fertilizer, etc. There are two types of green roofs, namely, intensive roofs and extensive roofs. Intensive roofs are thicker and can support a wide variety of plants but are heavier and require more maintenance than extensive roofs. Extensive roofs are typically covered with a light layer of vegetation and are hence lighter than intensive roofs.
Green roofs reduce storm water runoff, absorb about 70% to about 100% of rainfall on the roof, reduce heat loss in winter, reduce internal building temperature during summer, reduce energy costs, improve sound insulation for the building, improve the aesthetics of the building, and are beneficial for wildlife. Moreover, the vegetation on the green roof removes carbon dioxide and absorbs pollutants from the atmosphere, protects the green roof from ultraviolet (UV) light, thereby increasing the life span of the green roof, and increases the potential to score, for example, more than 7 leadership in energy and environmental design (LEED) credits under the Unites States (US) green building council certification system. Furthermore, evaporation from the vegetation cools the air around the green roof. Hence, there is a need for increased use of green roofs on buildings.
However, conventional green roofs incur high material and installation costs, for example, about 500% to about 1000% higher costs than traditional roofing costs. Moreover, conventional green roofs require stronger roof beams for supporting the extra weight of the vegetation and the growth media, incur high maintenance costs, and require complex drainage systems, thereby limiting their use primarily to expensive custom homes, large public buildings, and corporate headquarters. Furthermore, most homes typically have sloped roofs for which inexpensive and easy to install green roofs are not available. Furthermore, traditional roofing is utilitarian only and there is a need for green roofs that are also aesthetically pleasing.
Furthermore, there is a need for managing precipitation and runoff through the capture and use of frequent lower intensity rainfall, for example, for supplementing irrigation of the vegetation in the green roofs, for physical and biological filtering treatment of the precipitation for water quality treatment; and also for the delay, evaporation, and transpiration of this precipitation for hydromodification management. Hydromodification is the change to storm water runoff volume, magnitude, and duration caused by changes in land use. For example, changing land use from natural to residential can increase the speed and amount of rainfall runoff. Hydromodification can result in adverse effects to stream habitat, surface water quality, and water supply, while the associated stream erosion can threaten infrastructure, homes, and businesses. Many municipalities in the United States now require certain development or redevelopment projects to incorporate water quality treatment measures and hydromodification management measures to minimize stream impacts such as excess erosion and sedimentation. Therefore, there is a need for developing a hydromodification management function in a roof, which delays the more frequent, lower intensity rainfall, and allows volume reducing effects such as evaporation to occur.
Hence, there is a long felt but unresolved need for a roofing apparatus that can be used in a roofing system, which is inexpensive, easy to install, support, and maintain on sloped roofs, and that requires uncomplicated drainage systems, manages hydromodification, and can be configured in multiple aesthetically pleasing architectural styles.